A high-pressure synchronous system and a low-pressure synchronous system have been known as an activation system of a main generator in a power generation plant (see Patent Literature 1). In the high-pressure synchronous system, a main generator needs to be directly connected to a main transformer and an activation transformer needs to be also provided. On the other hand, according to the low-pressure synchronous system, while a main circuit switchgear is provided between a main generator and a main transformer, an activation transformer is not supposed to be required.
In the main circuit switchgear of a low-pressure synchronous system described in Patent Literature 1, a breaking part and a disconnecting part that are accommodated in a first metal container (a casing) are mounted on a support frame. That is, the breaking part and the disconnecting part are directly fixed onto a top panel that constitutes the support frame. Furthermore, accessory devices other than the breaking part and the disconnecting part such as a capacitor, an arrester, and an instrument transformer are mounted on a mounting plate, which is placed below the top panel of the support frame.